The testing machine for the looseness of the transverse load can be used to research looseness under the condition that the bolt bears horizontal alternating load, and the current testing machines for the looseness of the transverse load are classified into the following categories:
1. Junker Type Looseness Testing Method
For example, GB/T 10431-2008. A Junker type looseness testing machine primarily applies an alternating transverse load to a fastener that applies a pretightening force to enable the fastener to move transversely. This transverse motion causes relative swing between a bolt and a nut, thereby resulting in microscopic slip of a larger thread contact surface and rapid looseness of the fastener. This allows the fastener to loosen faster than any previous testing method.
2. Electro-Hydraulic Servo-Controlled Vibration Method
During test, a tested fastener is tightened on a clamping platform, and a specified pretightening force is produced. An alternating transverse displacement is produced between two clamped metal plates through a servo hydraulic cylinder, resulting in reduction or even loss of a clamping force. The instantaneous clamping forces are continuously recorded, and the anti-loose performance of the fastener is judged by comparison.
3. NAS Vibration Testing Method
A specimen is tightened into a test sleeve, and location marks are made on a part and the sleeve. Then, the sleeve is placed on a vibration testbed for moving back and forth. After starting, the sleeve impacts both ends of a guide groove back and forth in the guide groove, producing a large impact force and causing looseness of the specimen. During the test, the position change of the specimen is recorded with regular stop, and the anti-loose performance of the specimen is judged accordingly.
The above methods are feasible for some actual working conditions, that is, when some bolts mainly play a limiting role, the bolts only transversely move alternately within a fixed displacement. However, the methods are not applicable to the case where some bolts are used for transverse loading, i.e., the bolts are subjected to a fixed transverse force.
When the transverse load force F applied to the bolts during work is not changed, with the looseness of the bolts, the transverse displacement produced by the transverse load force F is always changed. However, in the Junker type looseness testing machine, a transverse displacement load A applied to the bolts is not changed. However, with the looseness of the bolts, a horizontal load produced by the transverse displacement load A is always changed. The two working states are contrary, and thus are not accurate. The testing machine shall ensure a fixed transverse load force, so as to better simulate single-bolt looseness during the work. At present, there is no patent related to a testing machine for looseness of a bolt transverse load. The testing machine is optimized based on this consideration.